Breathing assistance apparatus

ABSTRACT

In one embodiment, a nasal cannula is shaped to fit within a user&#39;s nares, where the nasal cannula includes at least one prong allowing high flow delivery of humidified gases and creates positive airway pressure in the patient&#39;s airway. The prongs have angled ends such that, in use, gases flowing through the prongs are directed to the user&#39;s nasal passages. The nasal cannula body is partially swivelling and preferably has a ball joint connector. In another embodiment the nasal cannula may have at least one flared end prong that preferably seals within a patient&#39;s nare.

INCORPORATION BY REFERENCE TO ANY PRIORITY APPLICATIONS

Any and all applications for which a foreign or domestic priority claimis identified in the Application Data Sheet as filed with the presentapplication are hereby incorporated by reference and made a part of thepresent disclosure.

BACKGROUND

Field

The present invention relates to apparatus for treating sleep apnoea.More specifically, the present invention provides a nasal positiveairway pressure device.

Description of Related Art

Obstructive Sleep Apnoea (OSA) is a sleep disorder that affects up to atleast 5% of the population in which muscles that normally hold theairway open relax and ultimately collapse, sealing the airway. The sleeppattern of an OSA sufferer is characterised by repeated sequences ofsnoring, breathing difficulty, lack of breathing, waking with a startand then returning to sleep. Often the sufferer is unaware of thispattern occurring. Sufferers of OSA usually experience daytimedrowsiness and irritability due to a lack of good continuous sleep.

In an effort to treat OSA sufferers, a technique known as ContinuousPositive Airway Pressure (CPAP) was devised. A CPAP device consists of agases supply (or blower) with a conduit connected to supply pressurisedgases to a patient, usually through a nasal mask. The pressurised airsupplied to the patient effectively assists the muscles to keep thepatient's airway open, eliminating the typical OSA sleep pattern.

The procedure for administering CPAP treatment has been well documentedin both the technical and patent literature. Briefly stated, CPAPtreatment acts as a pneumatic splint of the airway by the provision of apositive pressure, usually in the range 4 to 20 cm H.sub.2O. The air issupplied to the airway by a motor driven blower whose outlet passes viaan air delivery hose to a nose (or nose and/or mouth) mask sealinglyengaged to a patient's face by means of a harness or other headgear. Anexhaust port is provided in the delivery tube proximate to the mask.More sophisticated forms of positive airway pressure devices, such asbi-level devices and auto-titrating devices, are described in U.S. Pat.No. 5,148,802 of Respironics, Inc. and U.S. Pat. No. 5,245,995 ofRescare Limited, respectively.

U.S. Pat. No. 5,477,852 of Airways Ltd, Inc. discloses a nasal positiveairway pressure device that has a pair of nasal members each having acannula tip to be inserted into the nares of the patient. Each cannulais tapered from a substantially circular cross-section outside thepatient's nostril to a substantially oval cross-section at the tipinserted into the nostril. An inflatable cuff surrounds each cannulawith the interior space of the cuff communicating with the lumen of thecannula through at least one aperture in the sidewall of the cannula.The nasal members are connected to one or more flexible hoses that, inturn, are connected to a source of positive air pressure. In use,positive air pressure is supplied to each cannula tip through the airhoses and nasal members. The positive air pressure inflates the cuffs tohold the nasal members in place and to effect treatment. The nasaldevice of U.S. Pat. No. 5,477,852 is attached to headgear that islocated about a patient's head; this headgear could be considered bymany patients as cumbersome and uncomfortable.

Conventional nasal masks used for administrating CPAP treatment are alsoconsidered uncomfortable and cumbersome, and prior art nasal masks andthe like are noisy (due to air leaks). These disadvantages in many casesare a formidable obstacle to patient acceptance of such treatment.Therefore, a substantial number of patients either cannot toleratetreatment or choose to forego treatment. It is believed a substantialnumber of such patients could benefit from a nasal positive airwaypressure apparatus that is more convenient to use and comfortable towear, thereby resulting in increased treatment compliance.

As oxygen is supplied as a dry gas it is well known in the art to eitherheat and/or humidify gases before delivering them for breathing by apatient. In particular when delivering oxygen, or oxygen or air mixture,it has proven beneficial to humidify the gases first. In WO01/41854 ofVapotherm, Inc. a system is disclosed that allows the delivery ofhumidified oxygen through a nasal cannula. This system uses a narrowbore conduit and nasal cannula with a high resistance to gas flows,thereby requiring the oxygen be of a high pressure. Air, as well asoxygen can also be passed down the conduit and nasal cannula and it toomust be of a high pressure. This system allows the delivery of highflows of oxygen enriched air to the patient, but is limited in the flowsachievable due to the narrow bore of the cannula resulting in highresistance gas flow and excessive velocity and noise upon exiting thecannula. Furthermore, the narrowness of the nasal cannula in this systemallows easy expiration of gases between the prongs and nares andtherefore does not create any positive airway pressure.

Innomed Technologies, Inc. manufactures a nasal cannula device calledthe NASALAIRE™. In this device air or oxygen travels down a wide boreconduit to nasal cannula. The NASALAIRE™ creates a physical seal betweenthe nares and itself, and relies on the absence of leaks around itselfand the nares to deliver pressure supplied by a continuous positiveairway pressure (CPAP) blower to the airway of the wearer.

SUMMARY

It is an object of the present invention to provide a breathingassistance apparatus which goes someway to overcoming the abovementioned disadvantages or which will at least provide the public auseful choice.

Accordingly in a first aspect the present invention consists in abreathing assistance apparatus comprising:

nasal cannula, shaped to fit within a user's nares, and adapted todeliver said humidified gases to said user,

a pressurised source of gases,

transportation means adapted to, in use, be in fluid communication withsaid source of gases and said nasal cannula and adapted to in use conveysaid gases to said user,

wherein said nasal cannula including at least one prong allowing highflow delivery of said humidified gases and creating a positive airwaypressure in said patient's airway, said at least one prong having anangled end, such that in use, gases flowing through said prong aredirected to said user's nasal passages.

In a second aspect the present invention consists in a breathingassistance apparatus comprising:

nasal cannula, shaped to fit within a user's nares,

a pressurised source of gases,

transportation means adapted to, in use, be in fluid communication withsaid source of gases and said nasal cannula and adapted to in use conveysaid gases to said user,

wherein said nasal cannula are adapted to deliver said humidified gasesto said user, said nasal cannula including at least one prong allowinghigh flow delivery of said humidified gases and creating positive airwaypressure in said patient's airway, said at least one prong having an endthat is flared outwardly.

To those skilled in the art to which the invention relates, many changesin construction and widely differing embodiments and applications of theinvention will suggest themselves without departing from the scope ofthe invention as defined in the appended claims. The disclosures and thedescriptions herein are purely illustrative and are not intended to bein any sense limiting.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred forms of the present invention will now be described withreference to the accompanying drawings.

FIG. 1 is a block diagram of a system providing humidified continuouspositive airway pressure to a user as might be used in conjunction witha nasal cannula of the present invention.

FIG. 2 is a perspective view of a first embodiment of the nasal cannulaof the present invention.

FIG. 3 is a side view of the nasal cannula of FIG. 2.

FIG. 4 is a plan view of the nasal cannula of FIG. 2.

FIG. 5 is a prong end view of the nasal cannula of FIG. 2

FIG. 6 is an exploded view of the nasal cannula of FIG. 2.

FIG. 7 is a side view of a second embodiment of a nasal cannula of thepresent invention.

FIG. 8 is a side view of a third embodiment of a nasal cannula of thepresent invention.

FIG. 9 is a perspective view of a fourth embodiment of a nasal cannulaof the present invention.

FIG. 10 is a side view of the nasal cannula of FIG. 9.

FIG. 11 is an exploded perspective view of the nasal cannula of FIG. 9.

FIG. 12 is a front view of the prongs of the nasal cannula of FIG. 9.

FIG. 13 is an exploded side view of the nasal cannula of FIG. 9.

FIG. 14 is a side cross-sectional view of a fifth embodiment of thenasal cannula of the present invention where the connection between abody part and connector of the cannula includes a plurality of channels.

FIG. 15 is a cross-section through AA of the nasal cannula of FIG. 14.

FIG. 16 is a side cross-sectional view of a sixth embodiment of thenasal cannula of the present invention including a shield that protectsan outlet vent from inlet gases.

FIG. 17 is a cross-section through BB of the nasal cannula of FIG. 16.

DETAILED DESCRIPTION

Whether used in a hospital environment or in a home environment, thenasal cannula of the present invention will generally have associatedthree main pieces of apparatus. Firstly, an active humidifier, whichthat controls the temperature of a heater plate heating a body of waterto achieve a desired temperature and humidity of the gases beinghumidified. Secondly, a transport conduit from the humidifier to thepatient is also required, which is preferably heated to reducecondensation, or “rain out”. Thirdly, a cannula designed to fit into thenasal cavity and deliver humidified, pressurized gases. In particular,in one embodiment the nasal cannula of the present invention has twoflared end prongs that seal within a patient's nares, although in someembodiments the cannula may have a single prong. The cannula prongs areshaped such that a step is created between them so that the prongs abutthe user's nasal septum in use. Furthermore, the gripping action of thesides of the prongs to the user's septum in use prevents the prongs fromdislodging from the user's nares. In another embodiment the prongs ofthe nasal cannula are angled toward one another as well as having anangled profile at the outlet of gases, such that gases flow from theprongs flows back into the nasal passage and is not forced up into therest of the nasal cavity.

With reference to FIG. 1 a humidified Continuous Positive AirwayPressure (CPAP) system is shown in which a patient 1 is receivinghumidified and pressurised gases through the nasal cannula 2 of thepresent invention. The cannula 2 is connected to a humidified gasestransportation pathway or inspiratory conduit 3. It should be understoodthat delivery systems could also be VPAP (Variable Positive AirwayPressure) and BiPAP (Bi-level Positive Airway Pressure) or numerousother forms of respiratory therapy. Inspiratory conduit 3 is connectedto the outlet 4 of a humidification chamber 5 that contains a volume ofwater 6. The inspiratory conduit 3 may contain heating means or heaterwires (not shown) which heat the walls of the conduit to reducecondensation of humidified gases within the conduit. The humidificationchamber 6 is preferably formed from a plastics material and may have ahighly heat conductive base (for example an aluminium base) which is indirect contact with a heater plate 7 of humidifier 8. The humidifier 8is provided with control means or electronic controller 9 that maycomprise a microprocessor based controller executing computer softwarecommands stored in associated memory.

The controller 9 receives input from sources such as user input means ordial 10 through which a user of the device may, for example, set apredetermined required value (preset value) of humidity or temperatureof the gases supplied to patient 1. The controller may also receiveinput from other sources; for example, temperature and/or flow velocitysensors 11 and 12 through connector 13 and heater plate temperaturesensor 14. In response to the user set humidity or temperature valueinput via dial 10 and the other inputs, controller 9 determines when (orto what level) to energise heater plate 7 to heat the water 6 withinhumidification chamber 5. A flow of gases (for example air) is providedto the chamber through inlet 16 from a gases supply means or blower 15.As the volume of water 6 within humidification chamber 5 is heated,water vapour begins to fill the volume of the chamber above the water'ssurface and is passed out of the humidification chamber 5 through outlet4. Exhaled gases from the patient's mouth are passed directly to ambientsurroundings in FIG. 1.

The blower 15 is provided with variable pressure regulating means or avariable speed fan 20 which draws air or other gases through the blowerinlet 17. The speed of the variable speed fan 20 is controlled by theelectronic controller 18 (or alternatively the function of thecontroller 18 could carried out by the controller 9) in response toinputs from the controller 9 and a user set predetermined required value(preset value) of pressure or fan speed via the dial 19.

Flared Prong Nasal Cannula

A first embodiment of a nasal cannula of the present invention is shownin detail in FIGS. 2 to 6. Referring to FIGS. 2 and 6, the nasal cannula2 comprises three main components; the prong part 21, body part 22 andball connector 23.

The prong part 21 has two nasal prongs 24, 25, each of which aresubstantially shaped to follow the contours of the human nares and inuse are placed inside a user's nares. The prongs 24, 25 extend out froma hollow tubular body 26 that in use fits to the body part 22. Each ofthe prongs 24, 25 are integrally moulded with the tubular body 26 in aflexible plastics material or rubber, such as silicone, other thermosetelastomers or thermoplastic elastomers such as Kraton™. The prongs 24,25 are substantially oval tubular members that allow for a passage ofgases. In particular, as shown in FIG. 5, the prongs are oval in shapeand angled in the same manner as a human's nares. The prongs 24, 25 areangled toward one another (or toward the vertical axis Y) at the top 27,28 of the prongs and away from one another at the bottom 29, 30 of theprongs. Furthermore, the ends 31, 32 of the prongs flare outwardly andpreferably are formed such that the ends of the prongs are thinner incross-section than the rest of the prongs. The flared thinner sectionends 31, 32 of the prongs assist with the sealing of the prongs 24, 25in use within the user's nares. When in use and with gases flowingthrough the prongs the force of the gas pressure will force the prongends 31,32 to flare outwardly and seal against the inside of the user'snares.

The prongs 24, 25 each include a step 33, 34 formed along their lengths.Each of the steps 33, 34 are formed on the prongs 24, 25 in an opposingmanner such that in use, when the prongs are within a user's nares thesteps 33, 34 abut the user's nasal septum and form a ledge that preventsdislodgement of the prongs. The prongs 24, 25 also have protrusions 35,36 formed on their outer edges that abut the sides of the user's nares(opposite to the nasal septum). The protrusions 35, 36 assist inpreventing the dislodgement of the prongs, especially if the user moveshis or her head. The protrusions 35, 36 also maintain the prongs withinthe user's nares in a correct orientation such that in use gases flowthrough the prongs and directly up the user's nasal passages.

The body part 22 is a tubular passageway in which the prong part 21 isconnected at one end and a ball joint 37 at the other end. The balljoint 37 extends from the connector 23 and slots into a complementaryshaped (partial sphere) socket end 39. The body part 22 also has anumber of apertures 38 formed in it, which act as a bias flow outletvent. Therefore, any gases exhaled by the user through their nose willexit through the apertures 38.

The connector 23 is preferably connected to the inspiratory conduit 3(see FIG. 1) that supplies gases flow to the cannula 2. The inspiratoryconduit 3 may be moulded directly to the connector 23 or otherconnection mechanisms may be used, such as a friction fit formed betweenthe connector and conduit.

Although a ball and socket joint, as described above, between the bodypart 22 and connector 23 is preferred other connections may be utilised,such as a flexible piece of silicone, or other appropriate connection.The connection between the cannula body and connector must be able to beflexed or rotated to allow for the inspiratory conduit 3 to be movedwithout causing the dislodgement of the nasal cannula 2 from the user'snares.

In the preferred form of the nasal cannula 2 of the present inventionthe body part 22 and connector 23 are preferably made from a hard orrigid plastics material, such as polypropylene, polycarbonate or acetyl.In other forms the body part 22 and connector 23 may be of differentplastics materials to allow for increased slidability between theseparts.

The prong part 21 may be supplied in various different sizes such thatdifferent sized user's may remove an existing prong part and simplyattach a different sized flexible plastics prong part over the body part22.

To provide additional comfort for the user or ensure the nasal cannulaof the present invention do not fall from a user's nares, the nasalcannula may be used in combination with a headgear strap, which in oneembodiment is a small flexible tube. For example, FIG. 1 shows aheadgear strap 40 extending from the nasal cannula 2. The ends of theheadgear strap that attach to the cannula may attach to extensions (orloops) 41 on the body part 22 of the cannula shown in FIG. 2, or mayattach about other appropriate areas of the cannula, for example, aboutthe connector 23.

The abovementioned embodiment of the nasal cannula 2 of the presentinvention is preferably a wide bore pronged cannula used for high flowconditions.

A second embodiment of the present invention is shown in FIG. 7. In thisembodiment of the nasal cannula 42 the prongs 43, 44 are preferablysmall bore prongs for use with lower flow conditions. The prongs 43, 44are similarly shaped to the prongs 24, 25 detailed above, but may notseal in the same manner as the abovementioned prongs due to the smallersize of the prongs. In fact these prongs may not seal at all in usewithin the user's nares.

Furthermore, in this second embodiment the nasal cannula 42 is smallerand weighs less as it is only comprised of a prong body 45 and prongs43, 44, where the body 45 is connected to a small tube that is formedwith corrugations or bellows 48 that connect to an inspiratory tube orconduit 47 (similar to the inspiratory conduit 3 described above) thatreceives a supply of gases.

The corrugations of bellows 48 will bend or move when a weight or forceis placed on the cannula, thereby preventing dislodgement of the cannula42 from a user's face in use. In particular, the corrugations or bellows48 prevent transferral of the torque onto the cannula 42 when a usermoves his or her head.

The body 45 of the cannula 42 is provided with a number of apertures 46that allows for gases exhaled by the users to be expelled into theambient air.

The prong body and prongs of this embodiment of the cannula of thepresent invention are preferably formed a flexible plastics material orrubber, such as silicone, other thermoset elastomers or thermoplasticelastomers such as Kraton™.

A third embodiment of the nasal cannula of the present invention isshown in FIG. 8 where the cannula may be provided with corrugated orbaffled sections on the prongs. The nasal cannula 49 of this embodimentis similar to that of FIG. 2 but the prongs 50, 51 have a series ofcorrugations 52, 53 formed in them. The corrugations 52, 53 allow formovement of each of the prongs 50, 51 for a better user fit, and allowfor movement of the cannula 49 without causing dislodgement of theprongs from the user's nares.

Angled Prong Nasal Cannula

A fourth embodiment of the nasal cannula of the present invention isshown in FIGS. 9 to 13. The nasal cannula 60 has a similar constructionto the nasal cannula of FIG. 2 and comprises three main components; aprong part 61, body part 62 and ball jointed connector 63.

The prong part 61 preferably has two nasal prongs 64, 65, each of whichare substantially shaped to follow the contours of the human nares andin use are placed inside a user's nares. In some forms a cannula withonly one prong may be provided. The prongs 64, 65 extend out from ahollow tubular body 66 that in use fits to the body part 62, preferablyabout an extension 67 (as shown in the exploded view of the nasalcannula of FIG. 11). Each of the prongs 64, 65 are integrally mouldedwith the tubular body 66 in a flexible plastics material or rubber, suchas silicone, other thermoset elastomers or thermoplastic elastomers,such as Kraton™. The prongs 64, 65 are substantially oval tubularmembers that allow for a passage of gases.

In particular, as shown in FIG. 12, the prongs are oval in shape (toreflect the shape of human nares) and angled in the same manner as ahuman's nares. The prongs 64, 65 are angled toward one another (ortoward the horizontal axis X) such that angles .alpha. are formedbetween the midlines m, n through each respective prong 64, 65. Theangled profile of the prongs 64, 65 means that they are moreergonomically correct with a human's nares and may assist in directingthe gases flow from the prongs to the user's nasal cavities. The prongs64, 65 are constructed such that their cross-sectional width narrowscloser to the tip of each prong.

In the preferred form the prongs 64, 65 have an angled and profiled end76 (see FIG. 10). The angled ends 76 assist in directing gases flow tothe user's nasal passages.

Each of the prongs 64, 65 has a flange 73, 74 disposed about itscircumference. The flanges 73, 74 are at a position on the prongs 64, 65such that the each of the flanges rests against the outside of each ofthe patient's nares. The flanges 73, 74 do not extend inside the nares,but rest at the entranceway of the user's nares, and preferably seal thenares. In some users the flanges 73, 74 may extend within the user'snares and provide sealing of the nares. The flanges 73, 74 arepreferably thin flexible extensions that extend substantially completelyaround the circumference of the prongs 64, 65. The flanges 73, 74 arepreferably substantially elliptical in shape with one side (for example,side 89, which in use will abut the nasal septum of a user) of theflange extending out from each prong further than the other side of eachprong. There is a recessed area 88 on each of the prongs between theflange and the shaped ends of the prongs in which preferably in use theends of a user's nares rest.

The body part 62 is a tubular passageway in which the prong part 61 isconnected at one end and a ball joint 69 at the other end. The balljoint 69 extends from the connector 63 and slots into a complementaryshaped (partial sphere) socket end 70 on the body part 62. The body part62 may also have a plurality of apertures 71 formed in it, which acts asa bias flow outlet vent. Therefore, any gases exhaled by the userthrough their nose will exit through the apertures 71.

A shield 75 (illustrated by the dashed line in FIG. 10) may extend overthe bias vent 71 inside the body part 70 to prevent gases from theblower (gases supply 15) from interacting with the bias vent 71 and ventholes, causing noise in use.

In a sixth embodiment as shown in FIGS. 16 and 17 a nasal cannulawithout a prong part is shown, but that includes a shield similar tothat described above. In this embodiment a body part 90 and a balljointed connector 91 fit together as described above. The body part 90includes an expiratory vent shield 92 that extends down from the topwall 94 of the body part 90 and shields the outlet vent 93.

Referring back to FIGS. 10 to 13, preferably the ball joint connector 63is angled and extends into a swivelable connector 68. The swivelconnector 68 is capable in use of being connected to the inspiratoryconduit 3 (see FIG. 1) that supplies gases flow to the cannula 60. Theinspiratory conduit 3 may be moulded directly to the connector 68 orother connection mechanisms may be used, such as a friction fit formedbetween the connector 68 and the conduit 3.

In other forms of the present invention the ball joint connector 63 orthe ball joint 69 may have formed in it a plurality of channels. Oneexample of this is the embodiment of FIGS. 14 and 15. Such channelsallow there to be a leak when gases flow through the connector to thecannula and prongs. The channels are therefore capable of acting as abias flow and a separate bias flow out outlet (such as that outlet 71described above) may not be required.

In FIGS. 14 and 15 only a body part 82 and ball jointed connector 83 areshown. The body part 82 and ball jointed connector 83 join in a manneras described above, where the substantially half sphere shaped end 84 ofthe body part 82 receives the substantially half sphere shaped end 85 ofthe connector 83. The ends 84, 85 enable a rotation between the bodypart 82 and connector 83. In this embodiment two channels 86, 87 areformed in the connector end 85. Two channels are shown in thisembodiment but there may be only one or any number of channels.Similarly, channels may be formed in the body part end 84.

It is preferred that there is a ball and socket joint, as describedabove, between the body part 62 and connector 63, although otherconnections may be utilised, such as a flexible piece of silicone, orother appropriate connection. The connection between the cannula bodyand connector must be able to be flexed or rotated to allow for theinspiratory conduit 3 to be moved without causing the dislodgement ofthe nasal cannula 60 from the user's nares.

In the preferred form of the nasal cannula 60 of the present inventionthe body part 62, connector 63, ball joint 69 and swivel connector 68are preferably made from a hard or rigid plastics material, such aspolypropylene, polycarbonate or acetyl. In other forms these may be ofdifferent plastics materials to allow for increased slidability betweenthese parts.

The prong part 61 may be supplied in various different sizes such thatdifferent sized user's may remove an existing prong part and simplyattach a different sized flexible plastics prong part over the body part62.

To provide additional comfort for the user or ensure the nasal cannulaof the present invention does not fall from a user's nares, the nasalcannula 60 is preferably used in combination with a headgear strap. Thestrap may be similar to that shown in FIG. 1 with relation to the firstform of the nasal cannula 2. In this fourth form of the nasal cannula 60the body part 62 has headgear extensions 72, 95 that extend out from thebody part 70. The extensions 72, 95 each have a channel 77, 78 formed inthem that is capable of receiving an end 80, 81 of the headgear strap79. The strap ends 80, 81 in use are threaded through apertures(preferably two) and extend into and are held in the channels 77, 78. Inthis form the headgear strap 79 is made from a small diameter silicon,rubber or similar type material. Therefore, when the strap ends 80, 81are threaded through the apertures friction is created that maintainsthe straps within the apertures and prevents the straps from slippingfrom the cannula.

In other forms the ends of the headgear strap that attach to the cannulamay attach to extensions (or loops) 41 on the body part 22 of thecannula shown in FIG. 6, or may attach about other appropriate areas ofthe cannula, for example, about the connector 23.

What is claimed is:
 1. A mask assembly including a nasal cannula prongpart and a nasal cannula body part for delivering positive airwaypressure to a user in use, the mask comprising: the nasal cannula prongpart comprising a hollow body, an inlet opening of the hollow body, andfirst and second nasal prongs extending from the hollow body, the firstand second nasal prongs formed as a flexible single piece, a horizontaldirection of the nasal cannula prong part extending from the inletopening toward the first and second nasal prongs, a vertical directionextending perpendicular to the horizontal direction; the nasal cannulabody part comprising a central portion with at least one bias flow vent,an inlet, an outlet, and an outer surface having at least a left sidecurved portion and a right side curved portion, the left side curvedportion comprising a left side apex and the right side curved portioncomprising a right side apex, the outer surface having a first heightalong the vertical direction; a first headgear extension having a firstend, the first end of the first headgear extension connected to the leftside apex, the first end of the first headgear extension having a secondheight along the vertical direction at the connection between the firstend and the left side apex; a second headgear extension having a firstend connected to the right side apex, the first end of the secondheadgear extension having a third height along the vertical direction atthe connection between the first end of the second headgear extensionand the right side apex, wherein the second and third heights aresmaller than the first height; a headgear strap configured to maintainthe nasal cannula prong part in a position with the first and secondnasal prongs against a user's nares in use, the headgear strap havingfirst and second ends, the first end connected to the first headgearextension and the second end connected to the second headgear extension;and an inspiratory conduit connected to the inlet of the nasal cannulabody part and configured to deliver pressurized gases into the nasalcannula body part and the nasal cannula prong part for inhalation by auser in use.
 2. The mask assembly of claim 1, wherein the first andsecond head gear extensions extend from the left and right apexes,respectively, along a first direction laterally outwardly away from theleft and right apexes, then along a second direction, oblique relativeto the first direction, more toward a user's face in use.
 3. The maskassembly of claim 1, wherein the nasal cannula body part comprises anextension extending proximally from the outlet of the nasal cannula bodypart to a position more proximal relative to the first end of the firstheadgear extension.
 4. The mask assembly of claim 3, wherein theextension of the nasal cannula body part extends circumferentially alongthe outlet of the nasal cannula body part, adjacent to the first ends ofboth the first and second headgear extensions.
 5. The mask assembly ofclaim 3, wherein the inlet of the nasal cannula prong part fits aboutthe extension of the nasal cannula body part.
 6. The mask assemblyaccording to claim 1, wherein vertically lower portions of the nasalcannula body part and the nasal cannula prong part, extending transverseto the horizontal direction, are concave with respect to an enclosedspace between the nasal cannula body part and the nasal cannula prongpart, when assembled.
 7. The mask assembly of claim 1, wherein the atleast one bias flow vent comprises a flow vent outer surface, the flowvent outer surface being recessed inwardly from the outer surface of therigid mask body.
 8. A mask assembly for delivering positive airwaypressure to a user, the mask comprising: a nasal cannula body partcomprising a circular inlet, a central portion and an outlet with firstand second curved lateral sides, the outlet of the nasal cannula bodypart comprising an oblong shape having a major direction with a firstend at the first curved lateral side and a second end at the secondcurved lateral side, the outlet having a minor direction extendingtransverse to the major direction, the outlet having a first heightalong the minor direction; a prong part comprising a hollow body, aninlet, and first and second nasal prongs extending from the hollow body,the inlet of the prong part removably connected to the outlet of thenasal cannula body part; a first headgear extension having a distal endand a proximal end, the distal end of the first headgear extensionconnected to the nasal cannula body part at the first end of the majordirection, the distal end of the first headgear extension having asecond height smaller than the first height; a second headgear extensionhaving a distal end and a proximal end, the distal end of the secondheadgear extension connected to the nasal cannula body part at thesecond end of the major direction, the distal end of the second headgearextension having a third height smaller than the first height; aheadgear strap connected to the first headgear extension and the secondheadgear extension.
 9. The mask assembly of claim 8, wherein the firstand second head gear extensions extend from the left and right curvedlateral sides, respectively, along a first direction laterally outwardlyaway from the left and right curved lateral sides, then along a seconddirection, oblique relative to the first direction, and more toward auser's face in use.
 10. The mask assembly of claim 8, wherein the nasalcannula body part comprises an extension extending proximally from theoutlet of the nasal cannula body part to a position proximal relative tothe distal end of the first headgear extension.
 11. The mask assembly ofclaim 10, wherein the extension of the nasal cannula body part extendscircumferentially along the outlet of the nasal cannula body part,adjacent to the distal ends of both the first and second headgearextensions.
 12. The mask assembly of claim 10, wherein the inlet of thenasal cannula prong part fits about the extension of the nasal cannulabody part.
 13. The mask assembly of claim 8, wherein the headgear strapcomprises a flexible tube.
 14. The mask assembly of claim 8, wherein thenasal cannula body part comprises an outer surface, the outer surfacecomprising a curved recessed portion, recessed inwardly relative to asurrounding portion of the outer surface, the curved recess portioncomprising a plurality of apertures defining a bias flow outlet vent.15. The mask assembly of claim 14, wherein a lower major surface of thenasal cannula body part, extending between the first and second curvedlateral sides, is concave with respect to an enclosed space between thenasal cannula body part and the nasal cannula prong part.
 16. A maskassembly for delivering positive airway pressure to a user, the maskcomprising: a nasal cannula body part comprising a circular inlet, andan oblong outlet comprising an oblong shape and first and second curvedlateral sides, the oblong outlet having a first height at a locationbetween the first and second curved lateral sides; a prong partcomprising a hollow body, an inlet, and first and second nasal prongsextending from the hollow body, the inlet of the prong part removablyconnected to the oblong outlet of the nasal cannula body part; a firstheadgear extension having a distal end, the distal end of the firstheadgear extension connected to the nasal cannula body part at the firstcurved lateral side, the distal end of the first headgear extensionhaving a second height smaller than the first height; a second headgearextension having a distal end, the distal end of the second headgearextension connected to the second curved lateral side, the distal end ofthe second headgear extension having a third height smaller than thefirst height; a headgear strap connected to the first and secondheadgear extensions and configured to support the mask assembly againsta user's face in use.
 17. The mask assembly of claim 16, wherein thefirst and second headgear extensions extend from the left and rightcurved lateral sides, respectively, along a first direction laterallyoutwardly away from the left and right curved lateral sides, then alonga second direction, oblique relative to the first direction, and moretoward a user's face in use.
 18. The mask assembly of claim 16, whereinthe nasal cannula body part comprises an extension extending proximallyfrom the outlet of the nasal cannula body part to a position proximalrelative to the first end of the first headgear extension.
 19. The maskassembly of claim 18, wherein extension of the nasal cannula body partextends circumferentially along the outlet of the nasal cannula bodypart, adjacent to the distal ends of both the first and second headgearextensions.
 20. The mask assembly of claim 19, wherein the inlet of thenasal cannula prong part fits about the extension of the nasal cannulabody part.